DE9102926U1 - Air gap insulated front pipe - Google Patents

Description

Description

&bgr; Air gap insulated pre-pipe

&bgr; The invention relates to an air gap insulated front pipe as an exhaust line between

&bgr; Engine and catalyst of an automobile with the components specified in the preamble of the claim

ω 1 listed characteristics.

12 In a known front pipe of this type, the inner pipe is, for reasons of

13 Due to the reduction in mass, the wall is comparatively thin in order to extract as little heat as possible from the exhaust gas that is in direct contact with it. 15 It is made of high-quality material, in particular steel.

The inner pipe leaving the heat-insulating air gap

&eegr; surrounding jacket pipe is responsible for the thermal insulation function,

The support function for the inner pipe. For example, the jacket pipe has the

te connecting flange to the exhaust pipe of the engine, in particular

20 welded on. Likewise, the jacket pipe forms the spigot end of the

21 pre-pipe into the catalyst housing. The jacket pipe consists of simple,

22 inexpensive material, especially steel, and is for stability reasons

23 is comparatively thick-walled.

25 In the known front pipe, the inner pipe at the engine end is connected to the

2β jacket pipe is firmly connected, while at the other end, on the catalyst side,

27 is guided with a sliding seat in the casing tube. For this purpose, the casing tube has

28 a line extending over a certain length range

2s diameter constriction. The sliding seat enables

% Relative mobility between inner tube and jacket tube in axial direction of the

31 pre-pipe is required to compensate for the

32 different thermal expansions of inner pipe and jacket pipe to

33. These different thermal expansions are unavoidable

34 due to the different temperature levels of the inner pipe and the jacket pipe.

37 The exhaust system formed by the front pipe between the engine and the catalytic converter

It does not run in a straight line, but rather on the conditions of the

8 March 1991

&igr; irregularly winding paths adapted to the automobile body.

a occur between the inner and outer tube in the area of the sliding seat next to

3 axial forces, strong transverse forces that are difficult to predict mathematically, which

4 jamming accompanied by unpleasant noise or

5 can cause the sliding seat to jam. &bgr;

7 The invention is based on the object of providing the inner tube within the

8 casing pipe and to guide it so that it can be

&bgr; thermal expansion can move freely relative to the casing pipe.

&ohgr; This object is achieved according to the characterizing part of claim 1 by

n spacer elements arranged in the sliding seat area, which in addition to the

12 Longitudinal displacement provides additional angular mobility between inner

13 and casing tube. These spacers give the u sliding seat a function comparable to that of a self-aligning ball bearing.

is effectiveness, namely the inner pipe is positioned relative to the jacket pipe

not only move axially, but also around the bearing center

&igr;? can be adjusted by swiveling. This also makes the sliding seat insensitive

&igr;» against misalignment between inner and outer pipe as well as against

&igr;« Bending movements of the inner tube relative to the jacket tube.

21 A further development provides that a sliding seat designed in this way

22 not only at the catalyst side, but also at the engine side of the

23 front pipe is present. In this case, it is advisable to place the

24 between both ends of the front pipe a fixed connection is provided between 2s inner pipe and jacket pipe. Starting from this fixed

2&bgr; connection, the inner tube can move freely towards both ends

27 relative to the casing pipe. The compensation of thermal expansion

28 between the inner and outer tubes is thus distributed more or less evenly over two 2« sliding seats. This means that the possible interference in the sliding seat area is halved to a certain extent.

32 The angle movement in the sliding seat area allows

33 Spacer elements can be designed in different ways.

34 This design is illustrated in the figures

35 examples are explained in more detail. They show:

37 Fig. 1 is a schematic longitudinal section through the essential parts of the 3β pre-pipe,

8. March 1M1

&igr; Fig. 2 a section along the line H-Il through the front pipe in

2 engine-side sliding seat area,

3 Fig. 3 a cross section along the line HI-III through the

4 catalyst-side sliding seat with a different design s of the spacer elements,

β Fig. 4 a cross section along the line IV-IV through the front pipe in 7 a middle area between the two ends, where the inner pipe

&bgr; is firmly connected to the casing pipe, e.g. welded,

β Fig. 5 a longitudinal section through the catalyst-side end of the pre-pipe, where ω the spacer elements of the sliding seat are formed by a spring ring

you are,

12 Fig. 6 is a schematic sectional view analogous to Fig. 5 only of the

13 spring rings,

µ Fig. 7 is an overall side view of the spring ring.

ie The pre-pipe according to Fig. 1 consists essentially of a thin-walled

17 inner tube 1 and a supporting tube 1 and leaving a

is the air ring gap 2 surrounding, comparatively thick-walled jacket pipe

ie The inner tube 1 is made of a high-quality, the jacket tube 3 of a

20 less high-quality and therefore less expensive steel. In the area of

21 Motor end 4, the casing tube 3 is fixed with a mounting flange 5

22. The end 4 of the inner tube 1 is in the flange recess

23. At its catalyst-side end 6, the jacket tube 3 is inserted into the

24 schematically indicated catalyst housing 7 is introduced.

26 In the area of both ends 4,6 of the front pipe, the inner pipe 1 is fitted with a sliding seat

27 on the casing tube 3. The structural design of the sliding seats is

28 except in the longitudinal section of Fig. 1 particularly clearly in the

2β Sectional views of Fig. 2,3 and 5 can be seen. Essential component

&khgr; of this sliding seat is the presence of over the course of the

si annular gap 2 distributed spacer elements between inner tube 1

32 and jacket tube 3. These spacers create a

33 additional angular mobility between inner tube 1 and jacket tube 3 by

34 an imaginary sliding seat centre point 9 approximately in the area of the tube axis 8.

3β According to Fig. 1 and 2 are evenly distributed over the circumference in the inner tube

37 1 in radial direction 10 on the casing pipe 3 protruding, bead-like

these bulges 11 are formed. In the case of the embodiment shown

8 March 1801

t the bulges 11 form a longitudinally effective

&zgr; Line contact between inner pipe 1 and jacket pipe 3. The total of three

3 bulges evenly distributed around the circumference of the inner tube 1 11

4 may, however, also be designed in such a way that they merely

5 Form point contact between inner pipe 1 and jacket pipe 3, &bgr;

7 The spacer element can also be a separate element in the air gap 2

β between inner pipe 1 and jacket pipe 3 fixed spacer 13,

&bgr; It is expediently elastically flexible in the radial direction 10 of the pipe

10. This allows even with a surface-shaped system on the

11 jacket tube 3 the desired angular mobility of the inner tube 1 in the

12 Sliding seat area. In the embodiment of Fig. 1,3, the spacer 13

13 a covered opposite the jacket pipe 3 by a metallic cap 14

14 buffer bodies 15, for example made of steel wool. In the embodiment according to Fig. 3, three such buffer bodies 15 are evenly distributed around the circumference of the pipe

It is distributed between two elements surrounding the inner tube 1 and attached to it.

ir fixing rings 16,17 and also on the inner tube 1, for example

The ring segments 18 secured by a welded joint in

The circumferential direction is kept at a uniform circumferential distance from each other.

21 In the case of the embodiment of Fig. 5-7, the spacer 13 is a

22 Inner tube 1 concentrically surrounding spring ring 19. The spring ring 19 is on

23 the inner tube 1 is pushed on and lies with its radial direction 10 convex

24 outwardly projecting spring blades 20 under pre-tension on the

25 inner circumference of the casing tube 3. The spring ring 19 is a spring steel 2β sleeve. The spring lamellas 20 are connected by several

27 distributed around the circumference of the cuff, arranged in axial or

28 12 bridge webs extending in the pipe longitudinal direction are formed, through which the two &kgr; ring sides 21,22 of the spring steel sleeve are connected to each other.

To produce the spring effect, the spring ring 19 sits with its one,

31 catalyst side ring side 21 fixed on the outer circumference of the inner tube 1

32, while its radially outwardly curved spring blades 20 are in

33 Radial direction 10 effective preload pressure on the inside of the

34 of the jacket pipe 3. The ring side 22 of the spring ring facing away from the catalyst

35 19 has a distance in the radial direction 10 from both the outer circumference of the

37 inner tube 1 as well as from the inner circumference of the jacket tube 3 (Fig. 5).

8 March 1981

&igr; Approximately halfway between the ends 4,6 of the front pipe, the jacket pipe

2 3 three radially inward-standing beads bridging the air gap 2

3 23. There, the air ring gap 2 is interrupted and the jacket pipe 3 is

4 there with the beads 23 directly on the outer circumference of the inner tube 1. In the $ area of the beads 23 the inner tube 1 is welded to the jacket tube 3.

&bgr; This creates a firm connection between the two pipes 1.3

7, while the other two, in the area of the ends 4.6

&bgr; existing connections between inner pipe 1 and jacket pipe 3 to the

&bgr; with regard to their structural design, the sliding seats are limited.

10 In this way, the inner tube outside the fixing area 24 is

11 of this, so to speak, floating within the casing tube 3

12 stored.

8.MJrz1M1

List of reference symbols

1 inner tube

2 Air ring gap

3 jacket pipe

4 Engine end

5 Mounting flange

6 catalyst side end

7 Catalytic converter housing

8 Pipe axis

9 Sliding seat center point

10 Radial direction

11 Bulging

12 Pipe longitudinal direction

13 Spacer

14 Cap

15 buffer bodies

16 Fixation

17 Fixation

18 Ring segment

19 Spring ring

20 spring slats

21 Ring side

22 Ring side

23 bead

8. MJrz 1M1

Claims (1)

91175-1/11
March 8, 1991 5 Claims s 1. The exhaust system between the engine and the catalytic converter of an automobile &bgr; forming, air gap insulated pre-pipe with 10 - a thin-walled inner tube (1) and 11 - a support for the inner tube (1) and leaving an air gap 12 annular gap (2) surrounding jacket pipe (3), &eegr; wherein at one end (4,6) the inner tube (1) with sliding fit on the jacket tube U (3) is guided, is characterized by ie that the sliding seat by 17 - distributed over the circumference of the annular gap (2), ie - the inner tube (1) is spaced from the jacket tube (3) and &igr;» - additional angular mobility between inner (1) and jacket pipe so (3) ensuring spacer elements is formed. 22 2. Front pipe according to claim 1, 23 characterized by 24 that the inner tube (1) 2s - is fixed between the two pipe ends (4,6) on the casing pipe (3) and 26 - is guided at both ends with the sliding seat on the casing tube (3). 28 3. Front pipe according to claim 1 or 2, 2β characterized in that µg that a spacer element provides a point contact between the inner tube (1) and 31 jacket pipe (3). 33 4. Front pipe according to claim 1 or 2, 34 characterized by 35 that a spacer element forms a line contact between the inner pipe (1) and the jacket pipe (3). 38 5. Front pipe according to claim 4, 8. M&rz 1M1 0 &igr; characterized by 2 that the line contact runs approximately in the longitudinal direction of the pipe (12). 4 6. Front pipe according to one or more of the preceding claims, 5 characterized by &bgr; that a spacer element is formed by a direction towards the other tube (1,3) 7 protruding, bead-like bulge, particularly of the inner tube (1) s is formed. &iacgr;&ogr; 7. Front pipe according to one of claims 1 to 5, 11 characterized by 12 that the spacer element is a separate element in the air gap (2) between the inner tube 13 (1) and jacket pipe (3) arranged spacer (13). is 8. Front pipe according to claim 7, ie characterized by 17 that the spacer (13) is elastically flexible in the pipe radial direction (10) is trained. 20 9. Front pipe according to claim 8, 21 characterized by Z ₂ that the spacer is a buffer body (15) of elastically flexible 23 consistency, for example steel wool. 25 10. Front pipe according to claim 9, 26 characterized by 27 that the buffer body (15) is provided with a 28 metallic cap (14). 30 11. Front pipe according to claim 9 or 10, 31 characterized by 32 that several buffer bodies (15) are distributed over the pipe circumference between two 33 surrounding the inner tube (1), with axial spacing between them on this 34 fixed fixing rings (16,17). 36 12. Front pipe according to one or more of the preceding claims, 37 characterized by se that the spacer (13) is a concentrically surrounding the inner tube (1) 8 March 1081 &igr; spring ring (19). 3 13. Front pipe according to claim 12 4 characterized by & that the spring ring (19) is pushed onto the inner tube (1) and &bgr; spring blades (20) rest against the casing tube (3). &bgr; 14. Front pipe according to claim 12 or 13, &bgr; characterized by 10 that the spring ring (19) has a spring steel sleeve with several over the 11 Cuff circumference distributed in axial direction (12) 12 extending between two ring sides (21,22), radially outward 13 curved bridge webs which rest against the casing tube (3), while it rests with one ring side (21) on the inner tube (1). θ.Mtrz1M1